In recent years, as electronic devices such as a laptop PC, a mobile phone, and a mobile information terminal are increasingly becoming used for mobile purposes, there is a growing demand for reduction in size of the devices themselves in order to improve portability.
On the other hand, in order to increase an amount of information and improve visibility and operability, it is desirable that a display section and an operation section be larger.
Accordingly, development has been conducted in order to develop a foldable device that includes two housings joined together by a hinge structure so as to be openable and closable, as well as development of a bendable flexible module as a module to be included in such a housing. In particular, a so-called flexible display, which has a flexibly deformable display part, has been drawing great attention in recent years as a display module that is thin, light-weight, and bendable.
A foldable flexible device that includes such a flexible module can have a reduced projection area of the entire flexible device when the flexible device is closed (i.e., folded), and can have increased areas of a display section and an operation section when the flexible device is opened (i.e., unfolded), due to an increase in surface area of the flexible device.
However, the foldable flexible device has a problem that a flexible module and a housing become misaligned when the flexible device is folded and when the flexible device is unfolded. In order to absorb such a misalignment, various techniques have been proposed (for example, see Patent Literature 1).
(a) through (c) of FIG. 17 are views each illustrating a schematic configuration of a main part of a display device 300 disclosed in Patent Literature 1. (a) of FIG. 17 is a view illustrating a state in which the display device 300 is folded, the view including an enlarged view of the main part. (b) of FIG. 17 is a view illustrating the display device 300 which is being unfolded, the view including an enlarged view of the main part. (c) of FIG. 17 is a view illustrating a state in which the display device 300 is unfolded, the view including an enlarged view of the main part.
As illustrated in (a) through (c) of FIG. 17, Patent Literature 1 discloses, as a foldable flexible device, the display device 300 which includes, as a flexible module, a display panel 304 which is flexible. The display device 300 includes housings 301 and 302 which are joined together by a hinge section 303 so as to be openable and closable. The hinge section 303 has an independent structure which follows neither turning of the housing 301 nor turning of the housing 302. The hinge section 303 includes a protruding shaft part 305 which is maintained in a predetermined position even in a case where the housings 301 and 302 turn.
A circle 306, which is illustrated in (a) through (c) of FIG. 17, is a circle that (i) centers around a turning axis 303a, which is a center axis of the hinge section 303 and (ii) coincides with a shape of an outer periphery of the hinge section 303. In a case where (i) the turning axis 303a is a center, (ii) an intersection between the circle 306 and a surface of the housing 301 on which surface the display panel 304 is laid is a first intersection a1, and (iii) an intersection between the circle 306 and a surface of the housing 302 on which surface the display panel 304 is laid is a first intersection b1, a portion connecting between the first intersection a1 and the second intersection b1 is a bent part 304a (a flexion part) of the display panel 304. The bent part 304a of the display panel 304 expands and contracts as the display device 300 is folded.
In Patent Literature 1, the following structure is employed so that misalignment between the display panel 304 and each of the housings 301 and 302 hardly occurs between a state in which the display device 300 is bent and a state in which the display device 300 is unfolded. That is, Patent Literature 1 employs a structure in which, when viewed along the turning axis 303a, (i) the bent part 304a of the display panel 304 is not fixed to the surface of each of the housings 301 and 302 on which surface the display panel 304 is laid, and (ii) the bent part 304a has a length D which is set to be substantially equal to a diameter of the circle 306 as illustrated in (b) of FIG. 17 and, in a state where the display device 300 is unfolded, be slightly longer than a linear distance between the first intersection a1 and the second intersection b1 as illustrated in (c) of FIG. 17.